Filter containers by status.

A continuation of #7616.
Closes #7616.
Adds `docker ps --filter=status=(restarting|running|paused|exited)` option.

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)
So my opinion hasn't really changed.
I find updating a PR is more of a realistic step forwards than letting things slide a little.
But happy to join the general consensus - as already mentioned.
However personally I'd rather fix such simple things than have a joint lengthy discussion only to settle on forming yet-another-backlog (because they don't tend to get actualised).

@jfrazelle so yes, correct usage of stuff and things makes me a happy panda.

@fredlf Using some fundamagical tools (I like `git grep`), it's really not a big deal to fix this kind of stuff.